Apparatus for crimping thermoplastic yarn



March 22, 1966 c. e. EVANS ETAL APPARATUS FOR CRIMPING THERMOPLASTIC YARN Filed Feb. 2'7. 1961 ATTORNEY United States Patent 3,241,212 APPARATUS FOR CRIMPING THERMOPLASTIC YARN Cyril G. Evans and George A. Mobley, Spartanburg, S.C., assignors to Deering Millikan Research Corporation, Spartanburg, S.C., a corporation of Delaware Filed Feb. 27, 1961, Ser. No. 91,852 Claims. (Cl. 28-1) This invention relates to methods and apparatus for the treatment of thermoplastic yarn. More particularly, it relates to the heat treatment of thermoplastic yarn which contracts substantially in length by crimp development when heated.

It is often desirable to subject thermoplastic yarn to a heat treatment under relatively low controlled tension prior to use, e.g., in the manufacture of woven and knitted fabrics. Such a heat treatment tends to stabilize the yarn to selected dimensions and fabrics constructed from such stabilized yarn have less tendency to shrink or stretch in use. That such a stabilization step is necessary is probably due to the fact that latent stresses are produced in the yarn during the various processing steps to which it is subjected prior to final use, e.g., drawing, crimping or bulking operations. In use, these stresses manifest themselves by changes in the configuration of the yarn or products prepared therefrom. The purpose of the heat treatment is to release these stresses under preselected and controlled conditions.

The usual procedure for stabilizing yarn is to overfeed the yarn into a heat processing zone so as to heat it to a temperature between its glass point, i.e., its second order transition point, and its sticking temperature. The degree of overfeed is determined by the properties desired in the finished product. One of the most common types of thermoplastic yarn which is subjected to a stabilization step or post treatment is bulked or crimped yarn, i.e., yarn which has been subjected to some deformation, e.g., false twisting, stufiing box or edge crimping, to produce actual or latent crimp in the yarn when in its relaxed state. However, the thus treated yarn is seldom bulked or crimped exactly to the desired degree or is adequately stable as a result of the crimping or bulking step alone' However, merely heating at an elevated temperature while the yarn is unrestrained may produce too great a contraction, i.e., bulking or crimping. To achieve the desired degree of bulking, crimping or contraction, the yarn is therefore overfed a selected amount into a heat processing zone, which amount of overfeed is less than the amount the yarn would contract if it were completely unrestrained, e.g., in hank form.

Although the yarn thus heated under selected conditions of overfeed is restrained from contracting in length to the maximum extent, the tensions required to achieve this restraint are of a very low order. Problems therefore arise in continuously feeding the yarn into the heat processing zone, especially at high velocities, as the yarn tends to become entangled in the overfeeding device, rather than proceeding in the proper manner into the heat processing zone, due to the very low force urging the yarn into the heat processing zone. This difliculty is particularly evident if the heat processing zone comprises a contact-type, conduction heater and is acute when the heater comprises a narrow, elongated tube. However, such a heating device is one of the more efficient methods of transferring heat to yarn traveling at high velocity and is often preferred for this reason. The methods and apparatus of this invention are therefore directed to methods and apparatus comprising this type of heater.

Another problem which arises in the development of the crimp, particularly latent crimp, in multifilament yarn is that the yarn tends to band, i.e., several filaments cling together and their crimps remain in phase with each other, thus reducing the bulkiness of the yarn at that point. This problem increases in severity along with increased yarn velocities. The consequence of such bulking is an objectionable lack of uniformity in products prepared therefrom.

The methods and apparatus of this invention solve one or more of the above described problems.

It is therefore an object of this invention to provide methods and apparatus for overfeeding yarn into a tubular heat processing zone at low tensions.

It is another object to provide methods and apparatus for overfeeding multi-filament thermoplastic yarn at high velocity and under low tensions into a tubular heat processing zone.

It is a further object to provide methods and apparatus for eliminating banding. of crimped multi-filament thermoplastic yarn while developing or altering the crimp therein.

Still another object is the provision of methods and apparatus for drawing, edge crimping and. post treating a running length of yarn in a continuous operation.

Other objects will be apparent to those skilled in the art to which this invention pertains.

Specific embodiments of this invention will now be described with reference to the accompanying drawings.

FIGURE 1 is a diagrammatic view of an apparatus according to this invention showing principal parts and their relative location;

FIGURE 2 is a diagrammatic view of an alternate apparatus according to this invention incorporating drawing and crimping stages;

FIGURE 3 is an enlarged, broken longitudinal crosssectional view showing the terminal portions of the heater tube and the gas tube employed in the apparatus shown in FIGURE 1.

With reference to the drawings in greater detail, and in particular FIGURE 1, there is shown a supply package 1 for supplying a running length of yarn 2. Guide means 3 and 4 carry the yarn through a gate-type tension regulator 5 to a capstan yarn advancing means 10 consisting of a larger driven roll 11 and a smaller driven roll 12. Another idler roll 13 is provided in conjunction with driven roll 11 to keep the yarn positioned properly on yarn advancing means 10. Adjacent to yarn advancing means Ill is an elongated hollow tube 30, having an open end entrance 31 and an open end exit 32. Tube 30 is bent at 33 for compactness. A source of E.M.F. 36 is connected to tube 30 at points 37 and 38 by wires 34 and 35. A smaller tube 40 connected to a gas supply 41 is shown inserted in the open end 31 of tube 30. Tube 40 can be heated by a resistance wire 42, connected to a source of electrical current, not shown, and wrapped several turns around tube 40. A second capstan yarn advancing means 20, consisting of a larger driven roll 21 and smaller driven roll 22, is adjacent open end 32 of tube 30.

As shown in FIGURE 3, tube 30 can be provided with flared edges and 81 at open ends 31 and 32 to facilitate the passage of yarn 2 through tube 30.

Guide means 50 is provided to guide yarn 2 from yarn advancing means 20 to a take-up package 51, driven by suitable means, such as a surface driving roll 52.

The apparatus show within Section A of FIGURE 1 can be incorporated into a unitary drawing, crimping and heat processing apparatus as shown in FIGURE 2. In this modification, a drawing operation is provided by a pair of capstan yarn advancing means 60 and 63, positioned adjacent guide means 4, the former consisting of a pair of driven rolls 61 and 62 and the latter by a driven roll 64 and an idler roll 65. Adjacent yarn advancing means 63 is a suitable crimping or bulking apparatus,

shown schematically in FIGURE 2 as a blade 70, adjacent yarn advancing means 10, having an edge 71 of small radius of curvature, e.g., 2 to 20 ten thousandths of an inch, i.e. an arcuate edge.

As shown in FIGURE 3, when a multi-filament yarn 2, which crimps or bulks when heated, is overfed into open end 31 of tube .30, the gas emitting from open end 43 of tube 40 causes the individual filaments thereof to separate, causing the yarn to billow out into a loose structure, shown schematically as 2a. As the yarn becomes heated in tube 30, thus causing the filaments thereof to crimp or bulk, t-he overfed length is taken up as the yarn contracts in length and assumes a bulked or crimped condition shown schematically as 2b. The point in tube 30 at which the billowed condition 2a changes to the crimped or bulked condition 2b will depend upon several factors, including yarn velocity and the temperature of the gas emitting from tube 40 and the temperature of tube 30.

When employing multi-filament yarn in the apparatus shown in FIGURE 2, it is preferred to have the surfaces that yarn 2 contacts, prior to its passage over blade 70, flat, e.g., cylindrical, so that the yarn is spread out in the form of a ribbon as it passes over the edge of blade 70, thereby contacting more of the individual filaments thereof with the sharp edge 71 of blade 70. Gate-type tension regulator 5 can be replaced by any of the well-known types of tension regulators or, if sufi icient friction is present in supply package 1, a tension regulator can be eliminated. Smaller rolls 62, 65, 12 and 22 are preferably canted slightly with respect to the radial axis of larger rolls 61, 64, 11 and 21, respectively, so as to ensure that the yarn passing through yarn advancing means 60, 63, and does not become entangled. Smaller driven rolls 62, 12 and 22 are conveniently driven by a belt connection, not shown, to larger driven rolls 61, 11 and 21, respectively. Tube or the gas supplied by tube 40, or both, can be heated by any suitable means so as to heat yarn 2 as it passes through tube 30. Tube 30 can be of any length sufficient to heat the yarn to the desired temperature for a minimum of about /2 second, preferably to 2 seconds or more. A minimum of about 12 inches is usually required and lengths as great as 20 feet or more may be desirable or necessary at high yarn velocities. The diameter of tube 30 is preferably less than about inch, more desirably, about to inch, but greater than the overall diameter of the yarn being passed therethrough, e.g., so that the inside cross sectional area of the tube is about 2 to 3 or more times that of the diameter of the yarn as it enters. Tube 30 need not be of uniform inside diameter. For example, it is sometimes desirable, when processing multi-filament yarn, to have open end 31 somewhat narrower than initial portion 82 so as to increase the change in pressure due to the Bernoulli effect or to facilitate the billowing of the yarn at initial portion 82. Similarly, it is sometimes desirable to constrict somewhat terminal portion 83 of tube 30 so as to control the final diameter of yarn fixed by the heat processing, i.e., control bulking. If the tube 30 is heated by applying a voltage thereto, it is desirable to employ high resistance material in the construction thereof, e.g., stainless steel. If other direct means of heating tube 30 is employed or if it is heated indirectly, e.g., by hot air passing therethrough, it can be constructed of other materials such as glass, ceramics or chrome plated copper or brass. Although tube 30 is shown with a bend at 33, it can be a straight tube or formed into a series of coils, depending on the length of the tube and space considerations. Usually sharp bends are undesirable and should be avoided.

Tube is preferably a capillary tube, e.g., of an inside diameter of 0.01 to 0.05 inch, preferably about 0.02 to 0.03 inch, so that the gas is emitted from open end 43 thereof at relatively high velocity, thereby producing maximum turbulence at the initial portion 80 of tube 30. Its capillary length will depend on the volume of gas to be passed through it. A length of about 2 to 10 inches is usually satisfactory and does not restrict unduly the volume of gas passing therethrough. Open end 43 of tube 40 is preferably positioned near the inside surface of tube 30 so as not to interfere with the yarn as it enters open end 31 of tube 30. The longitudinal axis of open end 43 of tube 40 can be positioned parallel or obliquely of the longitudinal axis of the initial portion 82 of tube 30. The gas supplied to tube 40 by supply means 41 is preferably compressed air, although other gases substantially inert to the yarn being processed can also be employed, e.g., superheated steam or nitrogen. If tube 30 is heated, tube 40 can be mounted along the surface thereof thereby pre-heating the gas as it passes through tube 40 or tube 40 can be heated by separate means. Although tube 40 is shown in the drawings as positioned near the open end 31 of tube 30, it will be apparent that it can be mounted at any suitable point along tube 30, gaining entrance thereto by providing a hole in the wall of tube 30.

The drawing apparatus shown in FIGURE 2 is represented by the yarn advancing means 60 and 63. Such elements can, however, be replaced by any of the single or multi-stage elements of a drawing apparatus known in the art. Drawing ratios of from about 2:1 to 10:1 can be employed, depending on the yarn being drawn. Ratios of from about 3:1 to 5:1 are common for such a single stage drawing operation. To facilitate the drawing operation, roll 64 can be heated, although the heat generated by the drawing may suffice. It is desirable to have driven roll 64 constructed of a material such that it provides a heat sink, thereby ensuring uniformity of conditions. This modification is particularly desirable when employing an edge crimping apparatus subsequent thereto. Sharp edge 71 of blade 70 is then placed in close proximity to the hot surface of driven roll 64 so that the yarn is in a heated state as it passes over the sharp edge 71 of blade 70. For detailed descriptions of various methods of performing an edge crimping operation see US. Patents 2,919,- 534 and 2,921,358.

The tubular heat processing apparatus shown in the drawings is well suited for processing yarn going into the tube at velocities from as low as 20 yards per minute, and is especially valuable at velocities from about 40 to 200 yards per minute to as high as 300 to 400 yards or more per minute. The apparatus of FIGURE 2 can suitably be mounted on a frame such as those commonly employed in nylon drawing apparatus, e.g., a draw twister or draw winder.

In setting up the apparatus shown in FIGURE 1 for operation, a thermoplastic yarn is taken from supply package 1 through tension regulator 5 and then wrapped a sufiicient number of turns around rolls 11 and 12 of yarn advancing means 10 to ensure non-slippage and then into tube 30. The gas provided by tube 40 can be used to facilitate threading the yarn through tube 30. The yarn is then wrapped several turns around rolls 21 and 22 of yarn advancing means 20 to ensure non-slippage and thence to the take up package 51. The apparatus is set up, e.g., by a series of interchangeable gears, so that yarn advancing means 10 overfeeds the yarn to yarn advancing means 20 at a selected rate such that the desired degree of contraction is obtained in the yarn. The term contraction includes both actual reduction in length of the treated yarn and apparent reduction in length, caused by increased bulking of the yarn in a relaxed state.

In the modification shown in FIGURE 2, the selected undrawn or partially drawn yarn after leaving tension regulator 5 is wrapped several turns around rolls 61 and 62 of yarn advancing means 60 and then wrapped several turns around rolls 64 and 65 of yarn advancing means 63. The relative speeds of driven rolls 61 and 64 is adjusted, e.g., by a set of interchangeable gears, so that the yarn is underfed to yarn advancing means 63, e.g., in the usual range of a drawing operation. The yarn is then passed over edge 71 of blade and then wrapped several turns around rolls 11 and 12 of yarn advancing means 10. The relative speeds of driven rolls 64 and 11 of yarn advancing means 63 and is also adjusted, e.g., by a similar set of interchangeable gears, to provide a selected tension or contraction, e.g., 0.5% to 3% contraction. The driving means, not shown, for yarn advancing means 60, 63, 10 and 20 and for take-up package 51 is preferably of a variable drive type such that different yarn processing speed can be achieved without altering the speeds of these advancing means relative to each other. This can be accomplished by procedures well known in art.

The selected final yarn velocity is determined by the speeds of yarn advancing means 20 and take-up means 51, the latter merely being adjusted for proper pick-up of the yarn advanced by advancing means 20. The speed of yarn advancing means 10 is adjusted in relationship to the speed of yarn advancing means 20 so as to provide the desired degree of overfeed and permit the yarn to contract the desired amount, within a range such that very low tension is applied to the yarn as it passes between them. Depending on the yarn being heat processed and its capacity to contract, overfeeds of from about 1% to 25%, ordinarily 5% to 20%, can be employed. In other words, the overfeed should be such that the yarn is pushed or stuffed into the entrance of tube 30 rather than being pulled therein by the contraction of the yarn, thereby ensuring that the yarn is satisfactorily removed from the overfeeding yarn advancing means 10 rather than becoming entangled therein. The speed of yarn advancing means 63 is adjusted relative to the speed of yarn advancing means 10 so that a suitable tension is available for the crimping step, e.g., from 0.1 to 1.0 gram per denier. The speed of yarn advancing means 60 is then set relative to the speed of yarn advancing means 63 so as to provide the desired draw ratio.

The heat means used to heat the yarn as it passes through tube 30 is preferably activated before the yarn is passed at operating velocities through the apparatus. However, additional heat may have to be provided at high operating velocities if the yarn is to be heated to relatively high temperatures. Ordinarily it is desired to heat the yarn to about 100 to 225 C., e.g., 150 to 200 C., although longer heating times at, e.g., 80 C., or very brief heating times at, e.g., 250 C., may sometimes be preferred, depending on the glass and sticking temperatures of the yarn being processed. The velocities and volumes of gas provided by tube 40 can be varied over a wide range, so long as there is thus provided a volume of gas passing concomitantly with the yarn through tube 30 substantially in excess of the volume produced by windage alone, e.g., from a 10% increase, preferably at least a 50% increase, to a 2 or 3 fold or more increase. Air velocities in the tube varying from about 20 to 800 feet per minute and volumes varying from about 0.1 to 1.5 cubic feet per minute or more can be employed with satisfactory results. Although any volume of gas passed through tube 30 in excess of that caused by windage alone will assist the yarn therethrough, it is ordinarily preferred to provide gas of a volume and velocity such that the stream of gas passing concomitantly through tube 30 with the yarn has a linear velocity in excess of that of the yarn in the tube. Very high volumes and relative velocities which would tend to loop or snarl the yarn are unnecessary and not desired. The optimum gas volume will depend on the relative cross sectional areas of the tube 30 and the yarn passing therethrough and the optimum gas volocity will depend on the yarn velocity, among other things.

A wide variety of types and sizes of thermoplastic yarn can be employed in the heat processing apparatus of this invention, but is preferably multi-filament, e.g., nylon 6 and nylon 66, polyesters, e.g., Dacron, cellulose triacetate, polypropylene and polyvinyl alcohol. However, such apparatus is of greatest value employing multi-filament 6 yarn, e.g., 300 to 15,000, preferably 500 to 8,000 and more preferably 3,000 to 5,000 total denier, having a denier per filament of about 7 to 25, preferably 18 to 20, such as carpet or upholstery yarn, especially those which bulk or crimp when heated, either by development of latent crimp or by increasing the actual or apparent crimp therein. If desired, several ends of yarns from a multiplicity of supply packages can be combined and passed simultaneously through tube 30 and then taken up on one or a multiplicity of take-up packages. If the unitary apparatus shown in FIGURE 2 is employed, then undrawn or partially drawn starting yarn will be employed, in which case the undrawn starting deniers thereof can be substantially higher than the higher figures given above, e.g., 10,000 or more.

EXAMPLE Using the apparatus shown in FIGURE 2, undrawn multi-filament nylon 6 containing 68 filaments and a total denier of approximately 4,000 was drawn, edge crimped and heat processed. The draw ratio, between yarn advancing means 60 and yarn advancing means 63 was 3.58:1. Roll 64 was heated to about C. The edge 71 of blade 70 had a radius of curvature of 0.0005 inch. The speed of yarn advancing means 10 was adjusted in relationship to yarn advancing means 63 so as to permit a 1.2% shrinkage of the yarn after passing over the blade, i.e., their relative speeds were 0.988z1. The speed of yarn advancing means 10 was adjusted to advance the yarn at about 93 yards per minute. Tube 30 was a 6 foot stainless steel tube, bent as shown in FIGURE 1, with an inside diameter of inch. It had a resistance between points 37 and 38 of 0.13 ohm. 4.4 volts were applied between points 37 and 38 so as to heat the tube to about C. Tube 40 was a capillary tube of 0.023 inch inside diameter and supplied 0.265 cubic feet per minute of unheated air from a compressed air source maintained at 105 pounds pressure. The speed of yarn advancing means 20 was adjusted so that the yarn was overfed thereto at a rate of 14% by yarn advancing means 10.

The resulting yarn was tufted into a looped pile carpet containing 22 ounces of yarn per square yard which was then dyed a light green. Coverage was excellent, the backing was not visible, resiliency was outstanding, pile height was high, and there was no evidence of banding. The carpet was commercially acceptable in all its characteristlcs.

Employing the same apparatus set up in the same manner, yarn was passed into the development tube 30 at about 158 yards per minute. The air supplied by capillary tube 40 was heated to about 215 C. The yarn did not reach its sticking temperature because of the lowering of the above temperature due to the expansion of the air leaving tube 40 and the entrainment of outside air. Carpet prepared in the above described mannor from this yarn also had excellent characteristics.

What is claimed is:

1. Apparatus for processing a running length of thermoplastic yarn which contracts substantially in length by crimp development when heated, comprising a yarn supply means, yarn edge crimping means and a yarn take-up means, an elongate-d narrow tube with substantially unrestricted openings at its ends so as to permit yarn and a gas to pass freely and concomitantly therethrough, means to heat said tube to a selected temperature sufficient to heat said yarn while in said tube to a temperature between 100 and 225 C., compressed gas means positioned so as to provide a stream of gas through said tube in the direction of yarn flow of a volume substantially in excess of the volume caused by windage alone, yarn advancing means to positively overfeed said yarn into said tube at very low tension at a rate greater than the rate at which said yarn is withdrawn from said tube, and yarn advancing means to withdraw said yarn from said tube.

2. The apparatus of claim 1 wherein said tube has an inside diameter of between about and /2 inch and a length between 1 and 20 feet, said yarn advancing means overfeeding said yarn to said tube is driven so as to provide a linear velocity for said yarn of between about 40 and 200 yards per minute, and said compressed gas is air.

3. Apparatus for processing a running length of undrawn, multifilament thermoplastic yarn comprising a yarn supply means, a first yarn advancing means driven so as to underfeed said yarn from said yarn supply means to a second driven yarn advancing means at a rate to provide a selected draw ratio, said second yarn advancing means comprising a heated roll; edge crimping means comprising an arcuate edge immediately adjacent the heated surface of said heated roll, guide means to guide said yarn from said second yarn advancing over said tarcuate edge to a third yIarn advancing means, driven so as to overfeed said yarn into an elongated, narrow tube from 1 to 20 feet in length having an inside diameter between about and -"/s inch along substantially its entire length and substantially unrestricted openings at its ends so as to permit yarn and gas to pass freely and concomitantly therethrough, means to heat said tube to a selected temperature sufficient to heat said yarn while in said tube to a temperature between 100 and 225 C.; a source of compressed air positioned proximate to the yarn entrance to said tube so as to provide a stream of air through said tube entrance to said tube so as to provide a stream of air through said tube in the direction of yarn flow with a velocity in excess of the velocity of said yarn passing through said tube; a fourth driven yarn advancing means for withdrawing said yarn from said tube; and yarn take-up means.

4. The apparatus of claim 3 wherein said compressed air is heated.

5. The apparatus of claim 4 wherein said source of compressed air comprises a capillary tube inserted into the yarn entrance to said tube.

References Cited by the Examiner UNITED STATES PATENTS 2,520,202 8/1950 Frearson et al 2859.5 2,584,043 1/1952 Oberly 2872 2,874,446 2/1959 Sellers 2872 2,944,319 7/1960 Crouzet 2862 2,977,746 4/1961 Klein et al. 2872 3,003,222 10/1961 Pitzl 2872 3,055,080 9/1962 Claussen et a1. 28-1 3,077,724 2/1963 Stoddard et al. 57-34 3,106,442 10/1963 Compostella et -al. 2872 X 3,117,361 1/1964 Crouzet 2862 3,142,147 7/1964 Betsch 57157 X FOREIGN PATENTS 561,067 7/ 1958 Canada. 1,124,622 7/1956 France.

345,969 6/ 1960 Switzerland.

DONALD W. PARKER, Primary Examiner.

RUSSELL C. MADER, MERVIN STEIN, Examiners. 

1. APPARATUR FOR PROCESSING A RUNNING LENGTH OF THERMOPLASTIC YARN WHICH CONTRRACTS SUBSTANTIALLY IN LENGTH BY CRIMP DEVELOPMENT WHEN HEATED, COMPRISING A YARN SUPPLY MEANS, YARN EDGE CRIMPING MEANS AND A YARN TAKE-UP MEANS, AN ELONGATED NARROW TUBE WITH SUBSTANTIALLY UNRESTRICTED OPENINGS AT ITS ENDS SO AS TO PERMIT YARN AND A GAS TO PASS FREELY AND CONCOMITANTLY THERETHROUGH, MEANS TO HEAT SAID TUBE TO A SELECTED TEMPERATURE SUFFICIENT TO HEAT SAID YARN WHILE IN SAID TUBE TO A TEMPERATURE BETWEEN 100* AND 225*C., COMPRESSED GAS 